Most ear infections are characterized by inflammation. In general, this condition, referred to as “otitis,” is treated upon diagnosis to reduce the risk of such conditions as hearing loss, tinnitus, facial nerve palsy, mastoiditis, labyrinthitis, vertigo, and encephalitis. The majority of ear infections affect either the external or the middle ear.
Otitis externa (infection of the external ear) is primarily caused by bacterial infections (caused, for example, by Staphylococcus intermedius, Streptococcus spp., Pseudomonas spp., Proteus spp., and Escherichia coli). Normally, the external auditory canal is inhabited by a low concentration of bacteria, whose growth is largely inhibited by the slightly acidic pH and the build-up of cerumen (ear wax). Patients who scrape away the cerumen and epithelium leave an open wound characterized by a high pH, in turn establishing an environment favorable for bacterial infection. Furthermore, in patients whose ears are often submersed in water (due to swimming or sweating, for example), the skin swells and loses its natural acidic protection, therefore increasing the susceptibility of such patients to otitis externa. If untreated, infection of the external auditory canal may lead to inflammation of the middle and inner ear and may even spread to the pinna, periauricular soft tissues, or the temporal bone. Otitis externa often results in a large build up of cerumen that may actually plug the ear canal and result in temporary hearing loss and pain. Otitis externa is also a problem in domestic pets, and particularly in dogs with ear canals that are covered with the ear such as Cocker Spaniels.
Otitis media, a common ailment in children, is a painful condition characterized by inflammation of the middle ear and resulting from a bacterial (e.g., Streptococcus pneumoniae, Haemophilis influenza, or Moraxella catarhalis) or viral infection. More than two-thirds of children in the United States have had at least one episode of otitis media by the age of three. It has been reported that treatment of otitis media costs the United States healthcare system more than 5 billion dollars annually. Treatment of otitis media is critical, since otitis media is associated with significant childhood morbidity and is a primary cause of hearing loss in children. During episodes of otitis media, fluid accumulates in the middle ear or, as it is also known, the tympanic cavity.
Acute otitis media is a condition in which fluid accumulation in the middle ear is accompanied by signs or symptoms of ear infection (including both viral and bacterial etiologies). Such pathology may exhibit a bulging eardrum accompanied by pain or, in some instances, perforation of the tympanic membrane. Such perforations may also be accompanied by drainage of purulent material. In contrast, otitis media with effusion is typified by fluid accumulation within the tympanic cavity without signs of infection.
Both acute otitis media and otitis media with effusion may cause substantial pain as pressure increases, positively or negatively, within the confines of the tympanic chamber. Oral antibiotics, steroids, and antibiotic/steroid combinations have been utilized to treat otitis media. Antihistamine/decongestants have also been utilized in the treatment of otitis media with effusion.
The anatomical features of the middle ear define what can be described as a “sealed” chamber although pressure equalization is accomplished through the Eustachian tube. On its lateral border, the middle ear is effectively isolated from the external auditory meatus (in the absence of a punctured ear drum), by the tympanic membrane. Medially, the middle ear is effectively sealed from the inner ear by a bony wall and the round window. The posterior wall of the tympanic cavity communicates with a large, but effectively sealed mastoid antrum. Only the anterior wall of the middle ear contains a passageway for effective communication outside of the tympanic cavity. There, a natural pathway provided by the auditory or, as it is also known, the eustachian tube, provides communication with the nasopharynx.
During episodes of acute otitis media, the painful increase in middle ear pressure may naturally resolve through a resultant perforation of, and drainage through, the tympanic membrane. However, the increased fluid pressure associated with otitis media with effusion (OME) does not resolve via this mechanism. In fact, for those patients suffering otitis media for prolonged periods of time, and especially for those with significant associated hearing loss, myringotomy with the placement of a tympanostomy tube may be indicated as a means of equalizing middle ear pressure and in restoring normal hearing. Recently, laser surgery has also been utilized to provide an aperture through the tympanic membrane through which the fluid trapped within the middle ear may drain. Usually these artificial perforations of the tympanic membrane heal once the infection is resolved; however, in a significant number of patients the perforation does not heal resulting in hearing loss and increased susceptibility to middle ear infections. As used herein, a “middle ear infection” is a bacterial or viral infection of the middle ear or Eustachian tube. This term is used interchangeably with the clinical term “otitis media.”
Besides the perforations of the eardrum provided by infection (acute otitis media), myringotomy and laser surgery, the eustachian tube (the natural middle ear drainage path described above) provides potential drainage of fluid from the middle ear. Unfortunately, episodes of otitis media with effusion (OME) effectively eliminate this drainage path of relieving middle ear pressurization. Reduced patency of the eustachian tube is believed to be one of the primary causes of OME in pediatric patients. In fact, it is known that OME elevates eustachian tube opening pressure independent of other pathological conditions effecting this conduit. Several references have suggested that improving the patency of the Eustachian tube may aide in resolving otitis media.
Thus, there is still a need for additional antimicrobial compositions.